noun a structure that prevents something going from one place to another.

A device, structure, or material that obstructs or impedes. For instance, an insulator serving as a barrier to electricity.

In a semiconductor, the region of a pn junction that is free, or depleted, of charge carriers. This is a deprecated term, as are barrier layer, barrier region, or blocking layer. depletion layer, or space charge layer are the more proper terms to use for this concept.